Moisture absorption in unfilled and glass-filled, cross-linked polyester

The moisture uptake characteristics of unfilled and filled lyester resin at 60°C are reported. The objective was to determine the influence of filler on the moisture uptake properties of unfilled polymer. Diffusivity in the filled polyester is lower than in the plain resin. However, the filled resin absorbs significantly more water than unfilled polyester. Tensile load was found to have no effect on the water uptake in plain polyester. However, moisture absorption was affected by tensile load in 20% (by volume) bead-filled polyester and in SMC-R65. Increasing load increased the diffusion coefficient in SMC-R65. Combining rules predicted the diffusion coefficient in unloaded SMC-R65, but could not account for changes in diffusivity caused by tensile loading. In bead-filled polyester, the diffusion coefficient was accurately predicted when microstructural effects were accounted for.